Progress with the. MPIK / UW - PTMS in Heidelberg. Max Planck Institute for Nuclear Physics / University of Washington Penning Trap Mass Spectrometer

Transcription

1 Progress with the MPIK / UW - PTMS in Heidelberg Max Planck Institute for Nuclear Physics / University of Washington Penning Trap Mass Spectrometer TCP 010, Saariselkä, April 1, 010 David Pinegar, MPI-K Heidelberg

2 Part I: Motivation for Tritium / Helium-3 Mass Measurement Part II: Design of Our Experiment Part III: Recent Progress 4 distance ( μm) z distance ( μm) y x distance (μm) 0 y distance ( μm) x distance ( μm)

3 Part I: Motivation for the Tritium / Helium-3 Mass Measurement 3 H Beta-spectrum and m( e ) The KATRIN Main Spectrometer

4 KATRIN and M( 3 H) M( 3 He) measurements Independent mass difference measurements provide the KATRIN collaboration with an important independent check on systematic uncertainties. KATRIN expected sensitivity should give: m( e ) < 0. ev/c (90% C.L.) or (for example) 5 discovery potential for m( e ) = 0.35 ev/c The Mainz Neutrino Mass Experiment result: m ( e ).3 ev/c (95% C.L.)

5 KATRIN and M(3H) - M(3He) measurements 3 H 3 He e Neutrino mass effects the decay spectrum: e dn dt p m c E0 E E E 1 dp 0 The most precise mass measurements currently give E 0 from: m( 3 H) - m( 3 He) = (1.) ev/c Sz. Nagy, T. Fritioff, M. Björkhage, I. Bergström, and R. Schuch [006] (1.7) ev/c R. S. Van Dyck, Jr., D. L. Farnham, and P. B. Schwinberg [1993]

6 UW-PTMS and SMILETRAP M( 3 H) and M( 3 He) Measurements Q-Value [ev] FTICR Penning Traps Stockholm Seattle Spectrometers (Curie plots) Sz. Nagy et al. Europhys. Lett., 74, 404 (006)

7 Part II The Design of Our Experiment MPIK/UW Externally loaded double Penning trap Ion Source Valves Control Rods Ball Joint Beam Tube 1.5 m Liquid Helium Superconducting 6 T Magnet Translation Stage Penning Traps Field Emission Point Cryogenic Preamplifier 10 cm

8 The Design of Our Experiment Particle Trajectory Top Endcap Elecrode z ρ Ring Elecrode Particle Dynamics Confinement: Magnetic and electric fields: Hyperbolic electrodes give harmonic oscillator potential. Trap length scale d =.11 mm V 0 ~ 88 V Superconducting solenoid gives uniform B-field B = 5.3 T Frequencies for a singly charged, mass 3 u ion: + = 30 MHz Cyclotron frequency z = 4.0 MHz Axial frequency - = 300 khz Magnetron frequency Length scales for a singly charged, mass 3 u ion: r c = 4 m Minimum ``axial-coupled'' amplitude a z = 9 m Thermal amplitude r m = 4 m ``Sideband cooled'' limit Bottom Endcap Elecrode

9 The Design of Our Experiment S T O R A G E C A P T U R E E X P E R I M E N T

10 Cyclotron Frequency Detection Methods Direct: Electronic image-charge detection at the ion s cyclotron frequency Time-of-Flight: Measurement of cyclotron excitation by transfer of cyclotron energy into axial energy, with time-of-flight axial velocity read-out Continuous Indirect: Continuous axial frequency measurement to detect shifts from cyclotron excitation Cyclotron-Axial Mode Coupling: Coherent transfer of cyclotron amplitude/phase into axial amplitude/phase

11 Continuous Indirect Cyclotron Frequency Measurements Top Trap Bottom Trap Cryogenic Amplifier Room Temperature Amplifier Room Temperature Electronics Ring-Bias Voltage System Ring Correction Signals Cyclotron excitation is detected indirectly, by observing the ion's axial resonance: qv0 z Simple-harmonic axial motion (~4.0 MHz) md A feedback loop holds the ion's axial natural frequency constant. Small perturbations (mainly the anharmonic E-field term C 4 and the quadrupole B-field term B ) are adjusted to shift the axial frequency as the cyclotron energy changes. The error signal of the feedback loop is integrated to give the cyclotron-induced shift of the ion's axial frequency.

12 Continuous Indirect Cyclotron Frequency Measurements Axial Frequency Shift 0 ppb (1) carbon 6+ 7/19/0 0.1 ppb Cyclotron Drive Frequency - 45,93, Hz Mass ratio measurements are from cyclotron frequency comparisons in the stable B-field: qb c Free space cyclotron motion (~30 MHz) m As an RF dipole drive field is slowly swept in frequency, cyclotron excitation is triggered

13 Continuous Indirect Cyclotron Frequency Measurements UW-PTMS Example data: M( 4 He) cyclotron frequency residuals (Hz) ppb helium + carbon 6+ CFR = 0.999,349,50,35(5) time (hours) R.S. Van Dyck, Jr., et al., Phys. Rev. Lett., 004, 9, 080

14 Part III: Recent Progress Hundreds of hours of work with trapped ions Ion source: Tests of ion transmission to the trap electrodes External loading and trap-to-trap transfers: Planning, electronics tests, and simulations Trap position and tilt alignment: Testing with electron and ion beams Temperature and liquid helium stabilization and computer monitoring Extending the control of hardware by software!

15 Recent Problems Hardware setbacks and other time-eating vices: + Valuable parts and difficult assembly - Superconducting magnet/cryostats * They can be broken (shipping) * They can quinch (it is often a long story) - Custom vacuum flanges * They can leak * Soldering can take time + Custom software - Trade-offs between simplicity, flexibility, and automation of tasks + Working with ions takes time... - Anharmonicity due to: * Surface charge on electrodes * Unwanted ions + Custom electronics - Many degrees of freedom! - Cryogenic environment can present reliability problems + Tritium is radioactive...

16 Tritium is Radioactive!

17 1. Recent Progress 3. RF manipulation of 1 C 4+ ions 1. Load ions -> See electrical noise (incoherent detection). Initial ion cleaning -> See good axial resonance (coherent detection) 3. Lock the axial frequency -> Improved ion isolation & cleaning 4. And this is just the beginning. 4.

18 Measurements with 1C4+

19 Measurements with 1C4+

20 Measurements with 1C4+

21 Summary and Conclusion Achieved goals: Laboratory setup and commissioned at MPIK Test measurements with protons and 1 C 4+ External ion source tested Both traps loaded Good lock-loop performance and measurement of all ion normal modes Improved data acquisition automation High performance environment stabilization and monitoring system Remaining challenges: Isolation of single ions Trap-to-trap ion transport Precision work with 3 H and 3 He ions Tune-up and characterization of active B-field stabilization system Simultaneous measurement in both traps Characterize systematic uncertainties for mass ratio measurements More details see the poster by Christoph Diehl: The MPIK/UW-PTMS-experiment

22 Our MPIK / UW Collaboration Professors: Klaus Blaum Robert Van Dyck, Jr. Post-doc: David Pinegar Students: Christoph Diehl Martin Höcker Jochen Ketter Sebastian Streubel Former Contributors: Tomasz Biesiadzinski Caleb Hotchkiss Seth Van Liew Ryan Weh Steven Zafonte

23 Constraints on masses From KATRIN Design Report of 004